In digital imaging systems, color management is the controlled conversion between the color representations of various devices, such as image scanners, digital cameras, monitors, TV screens, film printers, marking devices, offset presses, and corresponding media. One of the primary goals of color management is to obtain a good match across color devices; for example, a video which should appear the same color on a computer LCD monitor, a plasma TV screen, and on a printed frame of video. Color management helps to achieve the same appearance on all of these devices, provided the devices are capable of delivering the needed color intensities.
Mapping of color spaces to the target color points of different target devices is used since many devices don't have the same gamut, or range of colors and brightness, that they are able to produce. For example, some colors outside of a target device's gamut need to be shifted to the inside of the gamut as they otherwise cannot be represented on the output device and would simply be clipped. For instance, printing a mostly saturated blue color as displayed on a monitor to a paper output using a typical CMYK printer will likely fail. The paper blue may not be that saturated. Conversely, the bright cyan of an inkjet printer may not be easily presented on an average computer monitor. The color management system can utilize various methods to achieve desired results and give experienced users control of the gamut mapping behavior.
Color mapping functions can be used to adjust the numerical values that are sent to, or received from, different devices so that the perceived color they produce remains consistent. A computer program that sends a signal to the computer's graphic card in the form RGB (Red, Green, Blue) 255,0,0, signals only a device instruction, not a color itself. This instruction then causes the connected display to show Red to the maximum achievable brightness, while the Green and Blue components of the display remain dark. The resultant color being displayed depends on two main factors: 1) the phosphors or crystals actually producing a light that falls inside the red spectrum and 2) the overall brightness of the color resulting in the desired color perception.
Every output device will have its unique color signature, displaying a certain color according to manufacturing tolerances and material deterioration through use and age. One challenge is dealing with a color that cannot be reproduced on a certain device in order to show it through a different device as if it were visually the same color, just as when the reproducible color range between color transparencies and printed matters are different. There is no common method for this process, and performance often depends on the capability of each color mapping method. There is no unique gamut mapping method that satisfies all requirements for image reproduction, such as pleasing color, contrast, lightness, chroma, hue, and the like. Some gamut mapping algorithms offer feature enhancements in one region of the gamut. Other gamut mapping algorithms do the same in other regions of the gamut. As such, device designers generally compromise in the gamut mapping functions they employ in their respective color management systems.
Accordingly, what is needed in this art are increasingly sophisticated systems and methods which automatically optimizes gamut mapping functions used to map input color points to points in a target gamut when rendering chromatic colors in the image path of a color management system.